With the progress of display technology, displays have been developed in the trend of slimness and planarization, and flexible displays (for example, foldable displays) have gradually become the next-generation displays. The flexible substrates are characterized by bendability, ease of carriage, compliance with safety standards, and extensive applications in consumer products. The flexible substrates also have large coefficient of thermal expansion and poor resistance to heat, moisture, oxygen, and chemicals. A flexible substrate may serve to hold electronic devices and/or act as a cover, so as to perform a packaging process on the electronic devices. Since the flexible substrate may not block permeation of moisture infiltration and oxygen, the moisture infiltration and the oxygen diffusion may speed up the aging process of the electronic devices on the flexible substrate. As a result, the lifetime of the electronic devices is shortened, and thereby the market demand cannot be satisfied.
A side wall barrier structure may be employed to enhance the ability of the flexible display to block moisture and oxygen. The side wall barrier structure is formed on the flexible substrate and is adhered to another flexible substrate by means of an adhesive. If the thickness of the adhesive between the side wall barrier structure and the flexible substrate is significant, the adhesion between the side wall barrier structure and the flexible substrate may be improved, whereas possibility of permeation of water vapor/oxygen increases.